Server-Client chat program

Question

I am writing a server-client chat program.

Here is my code

SERVER:

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class HelloServer {

    public final static int defaultPort = 2345;

    public static void main(String[] args) {
        int port = defaultPort;
        try {
            port = Integer.parseInt(args[0]);
        } catch (Exception e) {
        }
        if (port <= 0 || port >= 65536) {
            port = defaultPort;
        }
        try {
            ServerSocket ss = new ServerSocket(port);

            while (true) {
                try {
                    Socket s = ss.accept();

                    String response = "Hello " + s.getInetAddress() + " on port " + s.getPort()
                            + "\r\n";
                    response += "This is " + s.getLocalAddress() + " on port " + s.getLocalPort()
                            + "\r\n";
                    OutputStream out = s.getOutputStream();
                    out.write(response.getBytes());
                    System.out.write(response.getBytes());
                    InputStream in = s.getInputStream();

                    System.out.println("from client");
                    int z = 0;
                    while ((z = in.read()) != -1) {
                        System.out.write(z);
                    }

                } catch (IOException e) {
                }
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }
}

CLIENT:

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class SocketGetINetAdd {

    public static void main(String[] args) throws UnknownHostException, IOException {
        Socket socket = new Socket("192.xxx.x.xxx", 2345);
        InetAddress inetAddress = socket.getInetAddress();

        System.out.println("Connected to:: " + inetAddress.getHostName() + " Local address:: "
                + socket.getLocalAddress() + " Local Port:: " + socket.getLocalPort());
        BufferedInputStream bfINPUT = new BufferedInputStream(socket.getInputStream());
        int b = 0;
        OutputStream os = System.out;
        while ((b = bfINPUT.read()) != -1) {
            os.write(b);
        }
        OutputStream osNew = socket.getOutputStream();
        String s = "This Is The Client"; // data to be sent
        osNew.write(s.getBytes());
        os.write(s.getBytes());

}

I've connected them through my program.

But now I want to know How to send some data back to the server from client?

What would be the code for client(for sending data to server) and also the code for the server for showing the data received from the client on the console(server)?

P.S- I am a novice in network programming. Please do not criticize my coding style :P

Answer 1

You need threads. The client in this examples read the lines from the System.in and sends the line to the server. The server sends an echo.

In your real application you have to take a look of the encoding

Server

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class HelloServer {

    public final static int defaultPort = 2345;

    public static void main(String[] args) {
        int port = defaultPort;
        try {
            port = Integer.parseInt(args[0]);
        } catch (Exception e) {
        }
        if (port <= 0 || port >= 65536) {
            port = defaultPort;
        }
        try {
            ServerSocket ss = new ServerSocket(port);

            while (true) {
                try {
                    Socket s = ss.accept();

                    new SocketThread(s).start();
                } catch (IOException e) {
                }
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }

    public static class SocketThread extends Thread {

        private Socket s;

        public SocketThread(Socket s) {
            this.s = s;
        }

        @Override
        public void run() {
            try {
                String response = "Hello " + s.getInetAddress() + " on port "
                        + s.getPort() + "\r\n";
                response += "This is " + s.getLocalAddress() + " on port "
                        + s.getLocalPort() + "\r\n";
                OutputStream out = s.getOutputStream();
                out.write(response.getBytes());
                BufferedReader input = new BufferedReader(new InputStreamReader(s.getInputStream()));
                while (true) {
                    String line = input.readLine();
                    System.out.println("IN: " + line);
                    s.getOutputStream().write(("ECHO " + line + "\n").getBytes());
                    s.getOutputStream().flush();
                    System.out.println(line);
                }
            } catch (IOException e) {
                System.err.println(e);
            }
        }

    }
}

Client

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class SocketGetINetAdd {


    public static void main(String[] args) throws UnknownHostException, IOException {
        Socket socket = new Socket("localhost", 2345);
        InetAddress inetAddress = socket.getInetAddress();

        System.out.println("Connected to:: " + inetAddress.getHostName() + " Local address:: " + socket.getLocalAddress() + " Local Port:: " + socket.getLocalPort());
        new OutputThread(socket.getInputStream()).start();

        InputStreamReader consoleReader = new InputStreamReader(System.in);
        BufferedReader in = new BufferedReader(consoleReader);
        while (true) {                        
            String inline = in.readLine();
            if (inline.equals("by")) {
                break;
            }
            inline += "\n";
            socket.getOutputStream().write(inline.getBytes());
            socket.getOutputStream().flush();
        }
    }

    public static class OutputThread extends Thread {

        private InputStream inputstream;

        public OutputThread(InputStream inputstream) {
            this.inputstream = inputstream;
        }

        @Override
        public void run() {
            BufferedReader input = new BufferedReader(new InputStreamReader(inputstream));
            while (true) {
                try {
                    String line = input.readLine();
                    System.out.println(line);
                } catch (IOException exception) {
                    exception.printStackTrace();
                    break;
                }
            }
        }

    }
}

Answer 2

Use server stream

OutputStream os = socket.getOutputStream();

instead of client console output stream

OutputStream os = System.out;

at client side to write back to server.

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and at server side use client stream to read from client in the same manner.

InputStream in = s.getInputStream();

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I have already posted a sample code on server-client communication. Read it for your learning.